Female rats are resistant to 1,2-dimethylhydrazine (DMH) carcinogenesis, but not to azoxymethane (AOM) carcinogenesis. AOM was found to produce kidney tumors in female rats, while similar conditions failed to produce kidney tumors in males. Piperazine, a pinworm eradicator, lowered the incidence of colon tumors slightly and pinworm had no effect on colon carcinogenesis.